One big change in the Midwest landscape I’ve seen on my occasional visits over the last decade: Lots of wind turbines are being installed (hundreds and hundreds of them in Illinois so far, with many more coming). I shot this pair–just off Interstate 80 on the southern outskirts of Geneseo–as we blasted past (my brother Chris was driving) on Labor Day on our way from Iowa City back to the Chicago area.

Chris asked “how much power do those things put out?” My researches have uncovered the following: These two turbines are Vensys 77‘s, each rated with a generation capacity of 1.5 megawatts. How much is that? The math isn’t straightforward: how much power is actually generated depends on weather conditions; the turbines need wind, of course, but they’re apparently also sensitive to high temperatures. In practice, the generators at this site might produced enough power for about 1,000 homes. The city of Geneseo, population roughly 6,500, said before the turbines began operation in October 2009 that it expected the turbines to provide between 12 percent and 15 percent of the electricity the town needs.

And: How big are those things? Big. The rotor diameter, which I take to be the diameter of the circle swept by the turbine blades, is 77 meters. About 240 feet. The top of the tower is about 300 feet.

Some years ago right here in the Land of Lincoln our municipally owned electric utility struck a deal to buy a certain amount of wind power in exchange for the Sierra Club not standing in the way of building a new coal fired plant. Odd thing, we had to buy from a wind farm in Iowa, which we did. Now that the new power plant is built and on line, the utility is saying the wind is too expensive so we’re trying to get out of the wind deal. It’s a mess.

Marie, just from the quick look I gave to the Illinois wind project it seemed all this stuff is happening in a real hurry. Not that that’s *necessarily* bad. But in the case of Geneseo, they think that at some point they’re going to get “free” power; meantime, the wind turbines have had at least a few mechanical problems and don’t seem to work so well when the temperature tops 89 F. The jury will be out for a long time on how costly/cost effective the whole thing is.